Drafting compass



Nov. A23, 1948. B. R. CAMERON 4DRAFTING COMPASS Find Aug.. 14, 1945 4.. l|||l lllllzlilllr rllflllllllllllllll.VII

w www# Patented Nov. 23, 1948 UNITED STATES Y OFFICE.y j

` 2,454,305: itsri'rlno COMPASS Byron R. Cameron, Mount Vernon, Ill. Application August 14, 1945; serial Nc; Grams 2 Gl'ams. 1i.

The present invention relates to drafting compasses and is more particularly concerned with Compasses constructed to rotate the compass point around a center spindle with power derived from the instrument itself.

It is Well known to draftsmen who are frequently required to describe numerous circles with a drop compass for protracted periods that the work is tedious and especially fatiguing to the muscles of the thumb and index finger, usually employed to rotate the compass point.

The primary object of the invention is to provide a drop compass with integral parts located interiorly of the instrument and adapted to rotate the marking element or compass point after the compass is adjusted and centered.

Another object of the invention is to provide a compass of the aforesaid type, of simpler and more compact construction than that of prior devices.

With the foregoing and other objects and advantages in View, the invention consists of the novel construction and arrangement of parts hereinafter described and claimed.

In the accompanying drawings illustrating the invention,

Figure 1 is a longitudinal vertical section of the compass.

Figure 2 is a horizontal transverse section on line 2-2 of Figure 1.

Figure 3 is a side elevation of the plunger.

Figure 4 is a side elevation of the slotted guide for the pin in the plunger.

Like numerals in the description and drawings designate the same parts of construction.

I designates the compass point but an ink pen or a lead holder may be attached instead. The compass point is attached, by means of set screws 2, to a lug 3 projecting from the outer wall of an elongated, tubular sleeve 4 at a suitable point thereon. A thumb screw 5 is provided to adjust the compass point I in relation to the center B so as to describe circles of various radii. 'I'he center is removably mounted in the end of a tapered, round collar 1. The sleeve 4 is provided with interior threads 8 of suitable pitch and angle adapted to engage the pin I3 of the hereinafter described plunger I2 contained within said sleeve. This sleeve 4 is interposed between said collar 'I and an upper collar 9 provided with finger grips Il] for the index and ring fingers of the hand. Centered in an aperture II in said collar 9 is a vertically-disposed plunger I2 which `is cylindrical in form and elongated. At a suitable point between the head of the plunger I2 I Cl. 33H27) n in said upper collar and projecting centrally in and its lower extremity a pin I3 passes transversely through the plunger I2 and projects at each end. The length of the pin I3 is more than the diameter of the interior wall of sleeve 4 and is adapted to move up and down with the plunger I2. When the plunger I2 is in its normally raised position, as shown in Figure 1, the ends of the said pin I3 impinge the bottom of collar 9 and limit the upward movement of the plunger I2. Located beneath the cross-pin I3 is an annular Washer I4 adapted to move with the plunger I2 and to contain the top of a coil spring I5 which is enclosed in the sleeve 4. The coils of the spring I5 are adapted to pass the threads on the interior wall of the sleeve 4. Interposed between said spring I5 and the plunger I2 is a tubular sleeve I6 which is elongated to extend from collar 9 to the top of collar 7. This sleeve I6 is secured fast in the aperture II of collar and in a socket I'I in collar 1. It is provided longitudinally with oppositely disposed slots I8 adapted to receive and guide the pin I3 of the plunger I2 in the up and down movement. It will be understood that the slotted guide I8 merely prevents the cross pin of the plunger from rotating the collars 'I and 9.

The sleeve `4 is free to rotate between said collars 'I and 9, and rotary motion is imparted thereto by the ends of the plunger pin I3 which t in said thread 8.

In operation, it is merely necessary to grasp the nger grips I0 on collar 9 with the index and ring fingers, and press down on the plunger I2 with the thumb. Movement of the plunger I2 gradually compresses the spring I5 and causes the plunger pin I3 to act on the threads 8 inside of sleeve 4, thus rotating the sleeve 4 and the attached compass point I. The plunger I2 Will return to its original position under the influence of the spring I5. While the rotary movement of the sleeve 4 will be reversed on the up stroke, nevertheless the marking element I will continue to describe the circle.

Having thus described myinvention what I claim as new and desire to secure by Letters Patent, is:

1. A drafting compass, comprising a rotatable tubular sleeve provided eXteriorly with a compass point, upper and lower non-rotating co1- lars positioned in alignment with said sleeve and adapted to contain the sleeve, linger grips projecting from the upper collar, a center mounted in said lower collar, a vertical plunger centered said sleeve, and means located within said sleeve and adapted to rotate the sleeve, said means adapted to be operated by the up and down movement of said plunger.

2. A drafting compass, comprising an interiorly-threaded, rotatable tubular sleeve provided exteriorly with an adjustable compass point, upper and lower collars positioned in alignment with said sleeve and connected therewith to permit rotation of said sleeve, nger grips projecting from said upper collar, a center mounted in the lower collar, a coil spring contained within said sleeve and adapted to raise the plunger in said sleeve, a vertical plunger centered in said upper collar` and projecting above same kand being centered within the sleeve and encircled by said spring, an elongated, tubular sleeve, provid` ed with oppositely-disposed longitudinal slots, secured in said collars and adapted to prevent rotation of same, a transverse pin in said plunger provided with projecting ends engaging said 20 threads, the slotted sleeve being interposed between the plunger and the spring, and a movable washer on said slotted sleeve interposed between the said cross-pin and the top of the coil spring.

BYRON R. CAMERON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 951,255 McMurray Mar. 8, 1910 1,005,992 McMurray Oct. 17, 1911 1,201,209 McMurray Oct. 10, 1916 FOREIGN PATENTS Number Country Date 276,713 Germany Sept. 17, 1913 1,952 Great Britain, 1910 Jan. 26, 1910 

